Isothermal fatigue of an aluminide-coated single-crystal superalloy: Part II. Effects of brittle precracking

T.C. Totemeier, W.F. Gale, J.E. King

    Research output: Contribution to journalArticlepeer-review


    The effect of brittle coating precracking on the fatigue behavior of a high-activity aluminide-coated single-crystal nickel-base superalloy has been studied using hollow cylindrical specimens at test temperatures of 600 °C, 800 °C, and 1000 °C. Three types of precrack were studied: narrow precracks formed at room temperature, wide precracks formed at room temperature, and narrow precracks formed at elevated temperature. The effect of precracking on fatigue life at 600 °C was found to depend strongly on the type of precrack. No failure was observed for specimens with narrow room-temperature precracks because of crack arrest via an oxidation-induced crack closure mechanism, while the behavior of wide precracks and precracks formed at elevated temperature mirrored the non-precracked behavior. Crack retardation also occurred for narrow room-temperature precracks tested at 800 °C - in this case, fatigue cracks leading to failure initiated in a layer of recrystallized grains on the inside surface of the specimen. A significant reduction in fatigue life at 800 °C relative to non-precracked specimens was observed for wide precracks and elevated temperature precracks. The presence of precracks bypassed the initiation and growth of coating fatigue cracks necessary for failure in non-precracked material. No effect of precracking was observed at 1000 °C.

    Original languageEnglish
    Pages (from-to)363-369
    Number of pages7
    JournalMetallurgical and Materials Transactions A
    Issue number2
    Publication statusPublished - Feb 1996


    • aluminum alloys
    • brittle fracture
    • coated materials
    • crack initiation
    • failure (mechanical)
    • Fatigue of materials
    • fatigue testing
    • fracture mechanics
    • intermetallics
    • nickel alloys
    • oxidation
    • single crystals
    • aluminide coated single crystal superalloy
    • brittle precracking
    • crack retardation
    • oxidation induced crack closure mechanism
    • superalloys


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